Source Code for Module roslib.message

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 33  # Revision $Id$ 
 34   
 35  """ 
 36  Support library for Python autogenerated message files. This defines 
 37  the Message base class used by genmsg_py as well as support 
 38  libraries for type checking and retrieving message classes by type 
 39  name. 
 40  """ 
 41   
 42  import os 
 43  import sys 
 44  import rospkg 
 45  import roslib 
 46   
 47  import genmsg 
 48  import genpy.message #for wrapping get_message_class, get_service_class 
 49   
 50  # forward a bunch of old symbols from genpy for backwards compat 
 51  from genpy import Message, DeserializationError, SerializationError, \ 
 52       Time, Duration, TVal 
 53  from genpy.message import get_printable_message_args, fill_message_args 
 54  from genpy.message import check_type, strify_message 
 55   
 56 -def _get_message_or_service_class(type_str, message_type, reload_on_error=False): 
 57      ## parse package and local type name for import 
 58      package, base_type = genmsg.package_resource_name(message_type) 
 59      if not package: 
 60          if base_type == 'Header': 
 61              package = 'std_msgs' 
 62          else: 
 63              raise ValueError("message type is missing package name: %s"%str(message_type)) 
 64      pypkg = val = None 
 65      try:  
 66          # bootstrap our sys.path 
 67          roslib.launcher.load_manifest(package) 
 68          # import the package and return the class 
 69          pypkg = __import__('%s.%s'%(package, type_str)) 
 70          val = getattr(getattr(pypkg, type_str), base_type) 
 71      except rospkg.ResourceNotFound: 
 72          val = None 
 73      except ImportError: 
 74          val = None 
 75      except AttributeError: 
 76          val = None 
 77   
 78      # this logic is mainly to support rosh, so that a user doesn't 
 79      # have to exit a shell just because a message wasn't built yet 
 80      if val is None and reload_on_error: 
 81          try: 
 82              if pypkg: 
 83                  reload(pypkg) 
 84              val = getattr(getattr(pypkg, type_str), base_type) 
 85          except: 
 86              val = None 
 87      return val 
 88           
 89  ## cache for get_message_class 
 90  _message_class_cache = {} 
 91   
 92  ## cache for get_service_class 
 93  _service_class_cache = {} 
 94   
 95 -def get_message_class(message_type, reload_on_error=False): 
 96      if message_type in _message_class_cache: 
 97          return _message_class_cache[message_type] 
 98      # try w/o bootstrapping 
 99      cls = genpy.message.get_message_class(message_type, reload_on_error=reload_on_error) 
100      if cls is None: 
101          # try old loader w/ bootstrapping 
102          cls = _get_message_or_service_class('msg', message_type, reload_on_error=reload_on_error) 
103      if cls: 
104          _message_class_cache[message_type] = cls 
105      return cls 
106   
107 -def get_service_class(service_type, reload_on_error=False): 
108      if service_type in _service_class_cache: 
109          return _service_class_cache[service_type] 
110      cls = genpy.message.get_service_class(service_type, reload_on_error=reload_on_error) 
111      # try w/o bootstrapping 
112      if cls is None: 
113          # try old loader w/ bootstrapping 
114          cls = _get_message_or_service_class('srv', service_type, reload_on_error=reload_on_error) 
115      if cls: 
116          _service_class_cache[service_type] = cls 
117      return cls 
118